Name: How they saved the holes in Swiss cheese
Uploaded: 2026-01-20T17:38:22.000Z
Duration: 6 min 2 s
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Basic passive voice

For almost a century, it was accepted that the holes in Swiss cheese came from carbon dioxide produced by the fermentation bacteria that convert milk to cheese.

Adverbs of manner

And that that just sort of happened automatically.

It's what's all over the Internet, and it's almost true.

About 30 years ago, Swiss cheese makers started to notice that the holes, the technical term is eyes, were getting smaller and less frequent.

Special Specifically the scientists here at Agriscope, a Swiss government backed agricultural research facility, where for science, they have a lot of samples of cheese and more importantly, samples of the bacteria that make it skim milk.

And about 1 to 5 billion cells, lactic acid bacteria per milliliter.

They have a shelf life of about 10 to 14 days.

So all year round, every week, the cultures are freshly made and sent to our customers.

We have our collection of strains, but we are also producer for these cultures.

We have the genomes of almost all the bacteria that we have in the collection here.

And we know what parts of the genome are responsible for some effects on the cheese.

From the Beginning of the 20th century, the microbiologists went to the different dairies all over Switzerland and took the cheese and different products like whey or the natural whey cultures and isolated bacteria from there.

At that time, each cheese dairy had its own culture to produce its own cheese.

And each one of these cultures was the result of decades or centuries of evolution of selection.

Many of these dairies had to close down or they switched to the commercial starter cultures.

These bacteria that made up their cultures would have disappeared if they hadn't been collected.

All the strains of our collection are frozen at minus 80 degrees.

And for the most important ones, we also freeze dry them.

Each strain that we store here has a backup on another site.

So each cheese has its own unique bacterial culture stored in the archive back there and regularly produced in these bioreactors.

The difference between Emmental and Gruyere is partly to do with technique, but

All the bacteria that we have here in the collection are owned by the Swiss dairy industry.

To have a competitive advantage, our bacteria are not better than other bacteria, but

Some of the cheese types are legally protected and to do that they have to use some special bacteria.

We call them marker bacteria because they bear a very specific sequence of DNA that we are able to detect in the Cheese during the production, but

And by detecting this small piece of DNA, we are able to say, okay, this is the right cheese.

It turns out that cheese fraud is a thing.

There's a market for fake, cheap Swiss cheese and in everyday English, particularly in North America.

There's also no distinction between Swiss type cheese and the specific Swiss cheeses that are made here near the Alps, the ones that have legal protected status marks on the packaging.

So Swiss dairies can work with the researchers here.

They can order the bacterial cultures or just get advice, but

it is strictly just for the industry in Switzerland.

There are trade secrets here that are guarded carefully by and which I was not allowed to even see, let alone film.

We regularly develop new cultures together with the cheese industry.

But because you have always to wait the ripening time for the cheeses, it takes always several years to develop a new culture.

So a few years ago, the team here had to answer the question, why aren't there holes in the cheese anymore?

We produce here the cheese, but then they go down to the cellar.

Most of the cheeses have to age between 3 months and 12 months at several time points.

We take samples to analyze them in the laboratory.

For the analysis of the holes, we use X ray and we use also computer tomography.

But we also see the distribution in the cheese.

The bacteria that are responsible for making these holes produce propionate acetate and carbon dioxide.

And this carbon dioxide is produced in the cheese and aggregates all around impurities.

The more the bacterium produces this carbon dioxide, it accumulates and builds these holes.

These impurities capture the carbon dioxide and then a bubble forms and grows.

They found that the milk was too clean, so we didn't have any dust in it.

And this was because we had closed milking systems so the dust could not get into the milk.

So the milking process is hermetically closed now.

And in former times in the barn, you had always this hay dust everywhere.

We tried different particles to put into the milk to see if the holes are growing again.

And we really could see that the whole formation was dependent on the concentration of the hay powder we put in it.

It's only one milligram per thousand liters.

Modern food safety standards mean that milk is far cleaner now than it ever was in the past.

Without the tiny well, these days it's imperfections in the past, it would have been contaminants but without those, if the milk is perfectly clean, the holes just don't form.

And while those holes don't really affect the taste, they certainly affect whether Swiss cheese looks like Swiss cheese.